Pestle-and-mortar grinders



M. H. APPLEGATE PESTLE-AND-MORTAR GRINDERS Oct. 14, 1958 3 Sheets-Sheet 1 Filed June 5, 1957 Inventor Mv'waa/ g a, #45 WW Zllomeys' Oct. 14, 1958 M. H. APPLEGATE PESTLE-AND-MORTAR GRINDERS 3 Sheets-Sheet 3 Filed June 5, 1957 m\mtmaaxxmw Inventor M 1 W A Horn e ye United States Patent PESTLE-AND-MORTAR GRINDERS Morriss H. Applegate, Leeds, England, assignor t0 Herbert Alexander & Co. Limited, Leeds, England Application June 5, 1957, Serial No. 663,783

4 Claims. (Cl. 241-199) This invention relates to pestle-and-mortar grinders in which continuous rotation is applied to effect grinding by the pestle of material contained in the mortar.

The object of the invention is to provide a grinder of this type with a particularly effective grinding action, capable of effecting reduction to extreme fineness, and of a high rate of operation.

According to the present invention, a power-driven pestle-and-mortar grinder has both its pestle and its mortar positively driven in opposite directions and with the pestle rotatable faster than the mortar, the axes of rotation of these being parallel but ofiset with respect to each other.

The centre of the area of the mortar covered by the rotating end of the pestle follows a circular orbit round the inside of the mortar, of a radius equal to the offset distance between the axes of rotation, which of itself ensures that different parts of the material placed in the mortar are continually brought between the pestle and the mortar.

According to a further feature of the invention, the mortar is mounted so as to be free to assume an inclined position under the contact with it of the offset pestle. This inclination encourages retention under the pestle of the material being ground. Thus, the mortar may be freely mounted within a rotatable cylindrical support, of internal diameter greater than the external diameter of the mortaror of a carrier block in which the mortar is secured-with a resilient pad, e. g., of sponge rubber, in the support, on which pad the mortar rests. The pads yields as the mortar is forced by the pestle to its inclined position inside the support.

Further to assist direction of the material being ground to the action of the pestle, a scraper blade may be positioned to fit the interior surface of the mortar in the wider portion of the space surrounding the offset pestle, and to fill most of the cross section of that part of the space. The blade may be adjustable as to depth and inclination, to suit the position assumed by the mortar when the latter is resiliently mounted as indicated above.

One embodiment of the invention will now be described in detail with reference to the accompanying drawings, in which Figures 1 and 2 are sideand front perspective views respectively of a pestle-aud-mortar grinder according to the present invention;

Figure 3 is a part sectional view taken on the line 33 of Figure 2 to a larger scale, and

Figure 4 is a fragmentary section corresponding to part of Figure 3, showing the grinder converted for simple mixing operations.

In Figures 1 to 3 a mortar 1 is secured in a carrier block 2 which is freely mounted within a rotatable cylindrical support 3 lying within the base portion 4 of a housing 5. Depending from an overhung part 6 of the housing is a pestle 7 secured in a holder 8 integral with H a shank 9, the axis of which is parallel to but offset from the axis of the support 3.

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As shown in Figure 3, an electric motor 10 mounted in the back of the housing 5 is coupled up to a reduction gearbox 11 from which extend vertically upper and lower portions 12, 13 respectively of an output shaft. The upper portion 12 is rigidly connected by an adaptor 14 to a shaft 15 to which is secured a pulley 16 for driving through a belt 17 a pulley 18 secured to the top of a rotatable sleeve 19 in which the shank 9 is mounted. The lower portion 13 has a small gear 20 secured to it and this gear drives a large gear 21 which is secured to the base 22 of the support 3. The base 22 of the support is secured on a shaft 23 supported by roller taper bear-- ings 24 in a bracket 25 secured by screws 26 to lugs 27 projecting inwardly from the housings.

The underside 28 of the carrier block 2 is partspherical and rests on a resilient pad 29, in the support 3, which has an internal diameter greater than the external diameter of the block 2. The pestle 7 is free to be lifted clear of the mortar 1 by hand, there being pegs 30 projecting inwardly from the sleeve 19 into vertical keyways 31 in the shank 9. To lock the pestle in its operative position, the upper ends of the keyways 31 continue into horizontal extensions 32, so that a partrotation of the shank brings the pegs 30 into the extensions. The pestle 7 when locked in operative position presses the mortar 1 into the resilient pad 29 and, because of the offset position of contact the mortar is forced to an inclined position inside the support 3, the drive being transmitted from the sleeve 19 to the shank 9 by contact of the pegs 30 with the closed ends of the extensions 32.

The belt-and-pulley drive to the pestle is without speed change and the gears 20, 21 are selected to provide a suitably reduced rate of rotation of the support 3 in the opposite direction. The interior surface 33 of the mortar 1 is part-spherical and the end 34 of the pestle 7 corresponds, but is rounded off at its periphery, so that as the pestle and mortar rotate in their respective directions and at their respective speeds, the pestle fits the mortar at all positions of relative rotation between the two, and also at all positions of relative inclination of the mortar, which inclination is maintained by the rolling of the underside 28 of the carrier block 2 on the resilient pad 29. Thus, the centre of the area of the mortars surface 33 covered by the rotating end 34 of the pestle follows a circular orbit round the mortar, of a radius equal to the offset distance between the axis of the pestle 7 and the axis (now inclined) of themortar 1, ensuring that the material (not shown) placed in the mortar is continually brought between the pestle and the mortar. This radius is indicated by R in Figure 3 and the radius of the area covered by the pestle indicated by A.

A scraper blade 35 is positioned to fit the: interior surface 33 of the mortar 1 in the wider portion. of the space surrounding the offset pestle 7, and to fill most of the cross section of that part of the space, to assist direction of the material being ground (not shown) to the action of the pestle. The blade 35 is mounted adjustably as to depth and inclination on a stem 36 protruding from a boss 37 screwed into the housing 5, so as to suit the position assumed by the mortar when the latter is in inclined position.

The mortar 1 makes a slight taper fit with the block 2 ensuring that the mortar rotates with the carrier, and the pestle 7 may be similarly fitted in the holder 8 with holes 38 in the sides of the holder to permit insertion of a tool for removal or replacement of the pestle.

Agate, porcelain, hardened steel, or fused alumina are suitable materials for both the pestle and the mortar. The carrier block may be of hard wood or plastic, and the resilient pad may be of sponge rubber.

A suitable speed, for the pestle is three times that of the mortar, with the mortar and pestle of 4" and 2" diameter approximately, as are suitable for a sample grinder such as the one illustrated and described; but these relative speeds and dimensions are given by way of example only.

The grinder may be converted readily for simple mixing operations by removing the pestle 7 from the holder 8 and inserting in its place a stirrer 39 (Figure 4), which consists of a taper plug 40 to fit the holder 8 and two (or more) protruding rods 41 each having an end secured in the plug by means of a screw 42.. The mortar 1 and its mountingblock 2 are removed and replaced by a bowl 43 provided with an annular shoulder 44 by which it is supported on the support 3 with its bottom 45 located within the support, two (or more) pegs 46 protruding from the bowl below the shoulder to engage slots 4'7 appropriately formed in the rim of the support 3, whereby the bowl 43 is positively rotated by the support 3.

The diiferent rates of rotation of the stirrer 39 and the bowl 43 in opposite directions promotes thorough mixing of the contents of the bowl.

The stirrer may be of steel or other suitable materials, and the bowl may be of any of the materials that may be used for the mortar, being selected according to the particular working conditions prevailing.

What I claim is:

l. A power-driven pestle-and-mortar grinder having both its pestle and its mortar positively driven in opposite directions and with the pestle rotatable faster than the mortar, the axes of rotation of these being parallel but ofiset with respect toeach other, and the mortar being mounted so as to be free to assume an inclined position under the contact with it of the offset pestle.

2. A grinder comprising a rotatable cylindrical support adapted to receive a mortar, a pestle rotatable about an offset axis parallel to that of the mortar support, and means for driving the support and the pestle in opposite directions, the pestle faster than the support, the support containing a resilient pad on which the mortar assumes an inclined position under the contact with it of the offset pestle.

3. A power-driven pestle-and-mortar grinder having both its pestle and its mortar positively driven in opposite directions and with the pestle rotatable faster than the mortar, the axes of rotation of these being parallel but offset with respect to each other, .the mortar being mounted so as to be free to assume an inclined position under the contact with it of the otfset pestle, and a scraper blade being positioned to fit the interior surface of the inclined mortar.

4. A grinder comprising a rotatable cylindrical support adapted to receive a mortar, a pestle rotatable about an offset axis parallel to that of the mortar support, and means for driving the support and the pestle in opposite directions, the pestle faster than the support, the support containing a resilient pad on which the mortar assumes an inclined position under the contact with it of the oifset pestle, and a scraper blade'being positioned to fit the interior surface of 'the mortar in the Wider portion of the space surrounding the offset pestle, and to fill most of the cross section of that part of the space.

References Cited in the file of this patent UNITED STATES PATENTS 210,360 Rawlins Nov; 26, 1878 234,052 Morrell Nov. 2, 1880 2,502,908 Whitlock Apr. 4, 1950 2,651,581 Courtney Sept. 8, 1953 

